The present disclosure generally relates to fastener driving tools, and specifically to such tools designed to operate with fasteners of varying sizes. The present driving tool automatically adjusts to differently sized fasteners to reduce jamming, thereby making the tools easier to use and having more accurate fastener delivery.
Power fastener driving tools are well known. Conventional driving tools are usually portable and are powered pneumatically or by combustion. Sample pneumatic tools are described in U.S. Pat. Nos. 4,932,480; 3,552,274; and 3,815,475, all of which are incorporated by reference. Combustion powered tools are described in commonly assigned U.S. Pat. Nos. 4,403,722; 4,483,473; 4,483,474; 5,197,646; and 5,263,439, all of which are incorporated by reference.
Such tools incorporate a tool housing enclosing the power source, such as a pneumatic cylinder or a small internal combustion engine. In combustion tools, the engine is powered by a canister of pressurized fuel gas also called a fuel cell. Power is generated from expansion of compressed gasses, either by burning of fuel in a combustion chamber or expansion of air in the pneumatic cylinder. Conventionally, a reciprocating piston having an elongated driver blade is actuated by the power source to drive the fasteners into workpieces. In most tools, an interlock prevents firing of the tool unless a workpiece contact element at the end of a nosepiece, or nosepiece assembly, is pressed against a workpiece.
Typically, the fasteners are collated into a strip and positioned within a feed slot or track in a magazine for sequentially advancing each fastener into a driving position within a driving bore of the tool. A shear block or guide surface is provided between the magazine and the bore for separating one fastener from adjacent fasteners in the magazine while guiding the fastener into the bore as being driven. While the tool and the magazine can accommodate nails of different lengths, substantially short nails can occasionally slightly tip or tumble near the magazine feed slot as the fasteners are being driven due to tool orientation, vibrations and unwanted movements of the tool. Such movements cause inaccurate driving of the fasteners and sporadic jamming of the fasteners within the tool.
One way to reduce tumbling and/or jamming of short fasteners is to provide a pivoting flap or lever in the magazine and shear block for guiding different length fasteners. Exemplary models of a fastener-size adjustment device are described in commonly assigned U.S. Pat. Nos. 5,437,404 and 6,808,101, both of which are incorporated by reference. With both of the above-referenced patents, the adjustment device is pivotally connected to the shear block and care must be taken to insure that a gap between the fastener and the adjustment device does not exist. This gap causes the tumbling and jamming of the short fasteners within the tool. However, it is difficult to reduce the gap automatically based on different lengths of the fasteners, and occasionally a user has to rotate the adjustment device manually to clear and prevent the jamming of the short fasteners. Therefore, there is a need for improving the adjustment device to accommodate fasteners of different lengths and prevent the tumbling and jamming of the short or smaller fasteners as they are being driven without requiring manual user intervention.